MDEV-9428 NO_AUTO_VALUE_ON_ZERO is ignored when a trigger before insert is defined

fix the *other* fill_record() too, arrgh!

mysql-test/r/trigger_null-8605.result

@@ -318,9 +318,8 @@ id
 delete from t1;
 create trigger t1_bi before insert on t1 for each row begin end;
 insert t1 values (0);
-select * from t1;
-id
-0
+insert t1 (id) values (0);
+ERROR 23000: Duplicate entry '0' for key 'PRIMARY'
 drop table t1;
 create table t1 (a int not null, b int);
 create trigger trgi before update on t1 for each row do 1;

mysql-test/t/trigger_null-8605.test

@@ -336,7 +336,8 @@ select * from t1;
 delete from t1;
 create trigger t1_bi before insert on t1 for each row begin end;
 insert t1 values (0);
-select * from t1;
+--error ER_DUP_ENTRY
+insert t1 (id) values (0);
 drop table t1;
 
 #

sql/sql_base.cc

@@ -8728,7 +8728,8 @@ fill_record(THD *thd, TABLE *table_arg, List<Item> &fields, List<Item> &values,
     value=v++;
     Field *rfield= field->field;
     TABLE* table= rfield->table;
-    if (rfield == table->next_number_field)
+    if (table->next_number_field &&
+        rfield->field_index ==  table->next_number_field->field_index)
       table->auto_increment_field_not_null= TRUE;
     if (rfield->vcol_info && 
         value->type() != Item::DEFAULT_VALUE_ITEM &&